The lead concentration obtained from sea water samples of San Juan Channel, Washington was 0.2 µg/l or less. Leads isolated from Pacific and Atlantic pelagic clay sediments show an isotopic composition similar to that of manganese nodules from the respective oceans. The Pb206 content in the Atlantic lead was more abundant than that in the Pacific lead. This finding agrees with the postulate that the Atlantic lead was derived from rocks which contained high proportions of old granites and that the Pacific lead was from rocks containing high proportions of relatively young basalts.
Chow, Tsaihwa J.. 1958. "Lead isotopes in sea water and marine sediments." Journal of Marine Research 17, (1). https://elischolar.library.yale.edu/journal_of_marine_research/907